1. Field of the Invention
This invention relates to Giardia lamblia, a protozoan parasite that causes the diarrheal disease giardiasis in humans and other mammals. This invention relates to monoclonal and polyclonal antibodies which specifically bind to native and recombinant δ-giardin and β-giardin and the localization of the δ- and β-giardins within the ventral disc of Giardia lamblia trophozoites.
2. Description of the Relevant Art
Giardia lamblia (synonymous with G. duodenalis and G. intestinalis) is a bi-nucleate protozoan parasite that colonizes the upper part of the small intestine of humans and animals causing diarrheal disease. The study of Giardia biology and efforts to develop control strategies against the parasite have been greatly advanced by the complete sequencing of its genome (Morrison et al. 2007. Science 317:1921-1926). In order to maintain infection within the small intestine, trophozoites, the replicative stage of the parasite, must attach to the epithelial layer of the gut and to resist its peristaltic movement, bolus flow and continuous shedding of mucus and cells. Unlike other Diplomonadida, Giardia has a unique organelle, the ventral disc (Elmendorf et al. 2003. International Journal for Parasitology, 33:3-28), which is believed to play a key role in Giardia virulence by mediating attachment to host epithelial cells (Palm et al. 2005. Mol. Biochem. Parasitol. 141:199-207). The rigid structure of the ventral disc, also referred to as the adhesive or sucking disc, is supported by a spiral array of microtubules emanating from posterior flagellar bodies. Adjacent microtubules are connected to micro-ribbons and cross-bridges. In addition to highly conserved tubulin and actin components, the ventral disc is composed of proteins, identified as α-, β-, γ- and δ-giardins (Nohria et al. 1992. Mol. Biochem. Parasitol. 56:27-37). Of those, definite localization within the ventral disc has been shown only for β-giardin, also referred to as striated fibre assembline homolog (Crossley and Holberton. 1985. J. Cell Sci. 78:205-231; Elmendorf et al., supra; Holberton and Ward. 1981. J. Cell Sci. 47:139-166; Holberton et al. 1988. J. Mol. Biol. 204:789-795;). While giardins are components of the cytoskeleton, there are reports in G. muris that β-giardin may also be expressed on the trophozoite surface (Heyworth et al. 1999. Exp. Paresitol. 91:284-287) or associated with the ventral disc membrane in the bare zone (Palm et al., supra). Original conflicting evidence on the location of alpha giardins (the annexine homologs) has been resolved by the discovery of twenty-one different α-giardins that may be present on flagella, the ventral disc, or on the trophozoite surface (Weiland et al. 2005. Internatl. J. Parasitol. 35:617-626). It appears certain that α1- and α2-giardins are associated with the plasma membrane, and play some role in attachment of trophozoites to host cells (Aggarwal and Nash. 1989. Infect. Immun. 57:1305-1310; Wenmann et al. 1993. Parasitol. Res. 79:587-592; Weiland et al. 2003. Internatl. J. Parasitol. 33:1341-1351). Current knowledge of the γ- and δ-giardin localization in the ventral disc is limited. In recent studies it was shown that anti-recombinant δ-giardin antibodies preferably recognized the ventral disc and inhibited trophozoite binding to an inanimate surface (Jenkins et al. 2009. J. Parasitol. 95:895-899).
There is a need for diagnostic agents for specifically identifying G. lamblia trophozoites and for therapeutic agents useful for inhibiting or preventing attachment of G. lamblia trophozoites to host cells, to thereby inhibit, ameliorate, or prevent clinical giardiasis.